Add functional test to check neighboring magnetic layers

Core/StandardSamples/MagneticLayersBuilder.cpp

Core/StandardSamples/MagneticLayersBuilder.h

Core/StandardSamples/SampleBuilderFactory.cpp

Tests/Functional/Std/StandardTests.h

...s/ReferenceData/Std/MagneticRotationReflectivityMM.int.gz

...eferenceData/Std/MagneticRotationReflectivityMM_NC.int.gz

...erenceData/Std/MagneticRotationReflectivityMM_Tanh.int.gz

...s/ReferenceData/Std/MagneticRotationReflectivityMP.int.gz

...eferenceData/Std/MagneticRotationReflectivityMP_NC.int.gz

...erenceData/Std/MagneticRotationReflectivityMP_Tanh.int.gz

...s/ReferenceData/Std/MagneticRotationReflectivityPM.int.gz

...eferenceData/Std/MagneticRotationReflectivityPM_NC.int.gz

...erenceData/Std/MagneticRotationReflectivityPM_Tanh.int.gz

...s/ReferenceData/Std/MagneticRotationReflectivityPP.int.gz

...eferenceData/Std/MagneticRotationReflectivityPP_NC.int.gz

...erenceData/Std/MagneticRotationReflectivityPP_Tanh.int.gz